The present invention relates generally to an endless abrasive belt surface treating apparatus, or a wide belt sanding machine, and more particularly to an improved platen for such an apparatus having means for driving the platen along with the work-contacting portion of the abrasive belt in an oscillatory or epicyclic pattern while work is being carried through the machine. Specifically, the improved wide belt sander of the present invention employs a belt driving system having an oscillating platen portion, and with the nature of the active contact between the abrasive belt surface and the work surface being controlled in part by the motion of the platen.
Wide belt sanders utilizing stationary platens are known in the prior art, with one such system being disclosed in U.S. Pat. No. 3,832,807, Kiser et al, assigned to the same assignee as the present invention. Additionally, other such wide belt sanders with stationary platens are shown in U.S. Pat. No. 3,429,079 for example.
In a typical platen head wide belt sanding machine, there is provided a platen base forming a sanding head and with an endless abrasive belt trained over a plurality of rollers or drums, one of which is power driven, the balance being idlers. The platen is interposed between a pair of belt guiding rollers. In the present arrangement, the drive roller is preferably disposed at the upper apex zone of the belt, with the rollers or drums disposed on either side of the platen normally being idlers and adapted to move in an orbital path with the platen per se.
Typically, in the present device, work is fed into the machine by a feed system or conveyor assembly that comprises an endless horizontally oriented conveyor belt, the upper span or flight of which cooperates with pinch-rolls so as to grip the work and feed it through the machine at a uniform rate. During this operation, of course, the top surface of the work is arranged in contact with the abrasive belt. In order to accommodate and adapt the apparatus to workpieces having different thicknesses, the conveyor assembly is adjustable either upwardly or downwardly toward or away from the wide belt assembly, which is normally supported against the force or thrust of work arranged on the conveyor belt.
Wide belt sanding apparatus with adjustable conveyors are disclosed in U.S. Pat. No. 3,832,807 referred to hereinabove, and reference is made to the disclose in that patent for the details of conveyor design.